Embodiments of the present invention generally relate to methods, devices, and systems for measuring tilt and more particularly measuring tilt of a pendulum for measuring gravitational fields transverse to the Earth's gravitational field.
Precision gravimetry is used extensively in mapping the Earth's local gravity and is important in oil and gas exploration, mining and mapping temporal geological shifts, the determination of Newton's gravitational constant and gravitationally imaging opaque systems. Precision of the order of 1 mGal (1 Gal=1 cm/s2) to 1 μGal is needed for mapping geological variations. Both relative and absolute measurements are employed. A standard in the industry for absolute measurements is measuring interference fringes due to the free-fall of a corner cube in one arm of a Mach-Zehnder interferometer with a sensitivity of 100 μGal/Hz−1/2. More recent measurements employ atomic interferometry achieving precisions of 100 nGal after two days of integration. The most sensitive device so far is a superconducting sphere suspended in the field of a superconducting coil achieving 3 nGal resolution after one month integration or 1 nGal over one year.
For horizontal fields, the first precision measurement of G was performed by Cavendish in 1798 who found G to one part per hundred. Since then, many additional experiments for determining G have been performed. Precision gravimetry extends beyond looking at gravitational fluctuations in the Earth. Experiments ranging from measurements of the gravitational constant G to imaging the contents of a container are currently an active field of exploration. For horizontal fields, many experiments have been performed using torsion pendula, simple pendula, and atom interferometery. While various gravimeters have been proposed, still further improvements may be desired. For example, it may be desirable to provide a small, lightweight, simple to build, easily portable, and/or inexpensive gravimeter capable of measuring gravitational fields or density fluctuations that are transverse to Earth's gravitational field. Additionally, it may be preferable to avoid the need for vacuum, cryostat, and/or cold atom technology.